Many types of heat sealing mechanisms are disclosed in, for example, Patent Documents 1 to 3, including JP 04-317905 A. The known heat sealing mechanisms are configured to heat seal an opening of a tubular film in which content is accommodated, followed by heat fusion cutting, to form a film pack.
In the known heat sealing mechanisms for forming the film pack, when a diameter of the to-be-heat-sealed opening of the tubular film is large, the opening portion of the tubular film is forcibly narrowed to reduce a front width (left-right width) of the opening portion, and heat sealing of the opening portion is carried out with the width-reduced portion held between a rod-like or linear heater and a heater receiver facing the heater.
Incidentally, if the width reduction is not forcibly performed, the left-right width of the to-be-sealed portion of the tubular film remains larger than a left-right width of a film passage port of the film sealing mechanism. Accordingly, the left-right width of the to-be-sealed portion of the tubular film becomes larger than a left-right width of the heater, resulting in failing to heat seal both left and right ends of the film.
For example, with regard to the width reduction function, a portable toilet device, which is configured to heat seal a tubular film accommodating bodily waste therein using a film sealing mechanism installed in a vertically small space, is provided with a means for performing width reduction for the heat sealing while retaining the film so as not to cause the film to be removed from a feed roller and making a width (length) or a width-direction thickness of the width-reduced film substantially uniform. Such a configuration is not proposed in known heat sealing mechanisms to be listed below.
The reason for performing the width reduction when heat sealing the tubular film is as follows. If a length of the film opening portion to be heat-sealed is large, a heater to be used needs to have a corresponding length. When the length of the heater is increased, power consumption is correspondingly increased, which poses a problem that a power supply other than a commercial power supply, that is, a portable type comparatively compact and small capacity power supply such as a secondary battery or a stacked cell for car battery or a primary battery such as a dry cell cannot be used.
In such a case, when a device in which the tubular film to be heat-sealed is mounted is a portable or transportable toilet device, there occurs another problem that the toilet device can be used only a location where a commercial power supply is available.
Thus, in order to allow use of a short length heater that has less power consumption and that can be operable with a compact power supply, it is necessary to make a length (lateral (left-right) width when viewing the tubular film from front) of a portion to be heat-sealed shorter than the large opening portion of the tubular film. Moreover, it is not sufficient to only slightly reduce the left-right width, that is, unless the thickness of the width-reduced film is as uniform as possible, homogeneous heat sealing cannot be achieved.
In view of the above problem, there is proposed a technology that performs processing of reducing the length of the opening portion of the tubular film having the larger opening diameter before the heat sealing, that is, “film width reduction” so as to allow the heat sealing to be achieved with a short length heater.
As one of conventionally proposed width reduction mechanisms, there is known a complicated mechanism in which the opening diameter of the film is narrowed from both front-rear and left-right directions of the opening portion in a crossing manner. Such a complicated mechanism has not only a problem in that the mechanism is not accommodated in a space having a small vertical width but also a problem in that it is difficult to make uniform even the thickness of the width-reduced portion of the film whose seal portion after the width reduction is less likely to be uniform.
On the other hand, in the portable or transportable toilet device, a tubular film set in a toilet bowl in a folded manner is guided from a film passage port formed at a lower portion of the toilet bowl to a feed roller provided below the film passage port. The film passage port has a substantially circular or ellipsoidal shape, which is the same as a shape of an opening of the toilet bowl. However, the shape of the film passage port formed above the feed roller is substantially a rectangular shape as viewed from above, and, moreover, guide walls formed so as to extend continuously from the rectangular film passage port are flat upright walls. Thus, the effect of both the rectangular passage port and flat upright guide walls continuously extending from the passage port poses a problem in that the tubular film drawn into the passage port by rotation of the feed roller easily gather to both corners of the rectangular passage. This is one of the causes that prevent the width of the film opening portion from being made smaller than a width of the film passage port or smaller than a width of the left and right rollers.